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Dynamic analysis of an in-line arranged cylindrical chimney
Harazim, Petr ; Kanický, Viktor (referee) ; Salajka, Vlastislav (advisor)
The diploma thesis deals with the response of a steel smokestack structure to wind loads. A detailed computational model implementing the finite element method was created in accordance with the available drawing documentation. The new smokestack was placed next to an existing one, thus it can be assumed that these two structures will affect each other. The thesis also elaborates on the problems of aerodynamic and aeroelastic stability of the earlier smokestack; in particular, the occurrence of vortex shedding in resonance with eigenfrequency of the structure, with the use of the program ANSYS CFX. The evaluation of the structure includes survey of the strength and deflections of the structure. The calculations are in accordance with valid ČSN EN norms.
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Design of mobile stand for suspending of electrodynamic exciter for aeroelastic phenomena testing in aviation
Vojáček, Jan ; Löffelmann, František (referee) ; Navrátil, Jan (advisor)
This Bachelor thesis deals with the design of mobile stand for carrying out ground vibration tests in aviation applications. These tests mainly judge the tolerance of aircraft against flutter. The start of the thesis deals with the teoretical background of aeroelasticity together with the historical events that led to the origins of research of such phenomenons. The second part of the tesis clarifies the motivation for designing the stand through overview of simmilar equipment avaiable on the market and through introducing the equipment used at the aircraft testing laboratory at the Institute of Aerospace Engineering. Third part of the thesis states possible approaches to the overal design of the stand and then crosses over to the chapter that discusses the chosen solution of the design. At the end there are introduced the results of modal analysis. These results state the natural frequencies occuring in the range of frequencies that normally occur while testing.
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New Approaches in Numerical Aeroelasticity Applied in Aerodynamic Optimization of Elastic Wing
Navrátil, Jan ; Slavík, Svatomír (referee) ; Komárek,, Martin (referee) ; Hlinka, Jiří (advisor)
Aeroelasticita je nezbytná vědní disciplína zahrnuta do návrhu letounů. Zaměřuje se na předpovídání jevů, které vznikají vlivem interakce aerodynamických, elastických a setrvačných sil. Tyto jevy často vedou ke katastrofickým následkům, proto musí být prokázáno, že nevzniknou v rozsahu rychlostí ohraničujících letovou obálku. Aplikace moderních materiálů při konstrukci draku, spolu se snahou navrhnout aerodynamicky efektivní tvar křídel, vede ke zvyšování poddajnosti letounů. To má za následek změnu aerodynamických vlastností a také k výraznějšímu vliv na aeroelastické jevy, které mohou být vyvolány snadněji vlivem pohybů tuhého tělesa než v případě tužších konstrukcí. Aeroelastické jevy mohou vznikat v širokém rozsahu rychlostí zahrnujícím i transsonickou oblast. V této oblasti je ovlivněna zejména rychlost, při níž dochází k třepetání, a to vlivem nelineárních jevů v proudu. Běžné nástroje, které jsou založeny na lineárních teoriích, nejsou schopny tyto nelineární jevy popsat. Cílem práce je proto navrhnout, implementovat a otestovat nástroj pro výpočetní (numerickou) simulaci aeroelasticity. Nástroj má využívat řešič proudového pole, který je schopen předpovědět nelineární jevy. V práci je kladen důraz na simulaci statické aeroelasticity. V práci jsou popsány metody, které je nutno zahrnout do numerické simulace statické aeroelasticity. Dále je popsán vlastní nástroj a je provedeno zhodnocení konvergence statických aeroelastických výpočtů. Funkčnost nástroje byla ověřena na příkladech, kdy byly použity různé aerodynamické a strukturální modely. Nástroj byl také aplikován při aerodynamické tvarové optimalizaci poddajného křídla. Výsledky optimalizace a její výpočetní náročnost byly porovnány s případem optimalizace tuhého křídla. Na závěr je v práci prezentován příspěvek autora do výzkumu zaměřeného na zhodnocení vlivu časové synchronizace mezi CFD a CSM řešiči. Použitý testovací případ je transsonické obtékání křídla na začátku třepetání (flutteru). Výsledky byly srovnány s experimentálními daty poskytnutými NASA.
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VUT 081 Kondor aircraft aeroelastic analysis
Talanda, Tomáš ; Šplíchal, Jan (referee) ; Juračka, Jaroslav (advisor)
This master thesis deals with VUT~081~Kondor aircraft flutter analysis. This aircraft is being designed at the Institute of Aerospace Engineering, Faculty of Mechanical Engineering, Brno University of Technology. The thesis contains detailed aircraft description, natural frequency and normal modes computation as well as aircraft structure flutter analysis and critical flutter velocity determination. Some structure improvement recommendations have been given in order to increase the critical flutter velocity and to fulfil the CS-VLA regulation requirements.
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Design of mobile stand for suspending of electrodynamic exciter for aeroelastic phenomena testing in aviation
Vojáček, Jan ; Löffelmann, František (referee) ; Navrátil, Jan (advisor)
This Bachelor thesis deals with the design of mobile stand for carrying out ground vibration tests in aviation applications. These tests mainly judge the tolerance of aircraft against flutter. The start of the thesis deals with the teoretical background of aeroelasticity together with the historical events that led to the origins of research of such phenomenons. The second part of the tesis clarifies the motivation for designing the stand through overview of simmilar equipment avaiable on the market and through introducing the equipment used at the aircraft testing laboratory at the Institute of Aerospace Engineering. Third part of the thesis states possible approaches to the overal design of the stand and then crosses over to the chapter that discusses the chosen solution of the design. At the end there are introduced the results of modal analysis. These results state the natural frequencies occuring in the range of frequencies that normally occur while testing.
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Classical flutter analysis of low pressure steam turbine blade cascade using 3D boundary element method
Prasad, Chandra Shekhar ; Pešek, Luděk
In this paper study of aeroelastic stability in steam turbine rotor is carried out using boundary element method. A mesh free fluid\nsolver is developed for fast estimation of unsteady aerodynamic loading and to estimate the aerodynamic damping in 3D blade cascade. The aerodynamic damping is estimated in traveling wave mode. The unsteady incompressible flow field is modeled using 3D surface Panel method. The proposed methodology successfully estimates aerodynamic damping with acceptable accuracy the for the aeroelastic (classical \n flutter) analysis of 3D blade cascade. The simulated results are compared with experimental data. The simulated aerodynamic damping shows good agreement with\nexperimental results. The present methodology shows significant reduction in computational time over computational fluid dynamic solvers.
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Fast estimation of flutter parameters of steam turbine blades using boundary element methods
Prasad, Chandra Shekhar ; Pešek, Luděk
In the present paper the classical flutter parameters in turbomachinery cascade such as aerodynamic damping estimation using fast numerical method is described. The unsteady aerodynamic loading and the aerodynamic damping (AD) coefficient of the vibrating cascades is estimated by 2D boundary elementmethod such as source and doublet panel method (PM). To estimate the flutter parameters aerodynamic influence coefficient traveling wave mode (TWM)method is adopted. The experimental aerodynamic damping is compared against simulated results. The result demonstrate that potential flow based boundary elements method can estimate the AD with desired accuracy and less computational time.
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Self-excited oscillation properties of the profile NACA0015 in subsonic flow
Zolotarev, Igor ; Vlček, Václav ; Kozánek, Jan
Self-excited oscillations of the profile NACA0015 in subsonic flow were realized in the wind tunnel. The plunge support had the same elasticity for all experiments, the pitch support had seven different elasticity parameters. During our experiments different types of selfexcited vibration (flutter, stall flutter) were observed. Range of Mach numbers was M = 0.08–0.45, corresponding range of Reynolds numbers is Re = (1–5)·105, when the chord length is used as the characteristic dimension of the profile.\n
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